Modeling the kinematics of multi-axial composite laminates as a stacking of 2D TIF plies

Thermoplastic composites are widely considered in structural parts. In this paper attention is paid to sheet forming of continuous fiber laminates. In the case of unidirectional prepregs, the ply constitutive equation is modeled as a transversally isotropic fluid, that must satisfy both the fiber inextensibility as well as the fluid incompressibility. When the stacking sequence involves plies with different orientations the kinematics of each ply during the laminate deformation varies significantly through the composite thickness. In our former works we considered two different approaches when simulating the squeeze flow induced by the laminate compression, the first based on a penalty formulation and the second one based on the use of Lagrange multipliers. In the present work we propose an alternative approach that consists in modeling each ply involved in the laminate as a transversally isotropic fluid – TIF - that becomes 2D as soon as incompressibility constraint and plane stress assumption are taken into account. Thus, composites laminates can be analyzed as a stacking of 2D TIF models that could eventually interact by using adequate friction laws at the inter-ply interfaces.Peer ReviewedPostprint (published version

A Natural Language Search Interface for Accommodation Queries

Services that once required human interaction are now completed with the click of a few buttons. In general, this allows for a more streamlined process for activities such as sending messages (email or text messages), filing taxes, or even shopping for groceries. In terms of searching for hotels and travel accommodations however, this process has not proven to be the most effective as the speed and efficiency is hindered by the interface through which this information is available. Choosing a travel specific site, filling in the required fields, combing through results for the desired specifications, and then possibly repeating the process elsewhere, does not provide the ability for the user to express the entirety of their preferences for the accommodation and is therefore not an effective method for searching. Natural language search provides a more accessible and intuitive interface for accommodation searching. Instead of specifying fields that may not encompass the the entirety of the desired search, the user is able to express all of the aspects in a single, natural language, search. In this project, we propose a natural language search interface for accommodations such as hotels, hostels, or apartments. Data acquired through Amazon Mechanical Turk is used to create a system for extracting various accommodation fields. Zilyo and Expedia APIs are then queried for real-time accommodation listings. These results are then adjusted based on the specifics of the search that were not included in the original query. A natural language search of this kind is not only more accessible on the consumer end, but provides data that pertains directly to the the entirety of the intended search

Assessing the web-portal type of eGovernment structures and measuring their socio-economic impact on the French Metropolitan Park

The use of eGovernment structures is becoming increasingly popular among public agencies due to the democratization of the Internet Communication Technologies (ICTs). Its application and impact at the public metropolitan level are however not widely studied, especially in France where the concept of the metropolis is relatively new. This research aims at assessing the degree of eGovernment development in the French Metropolitan Park, by developing an eGovernment Development Score (eGDS) focused on web-portal analysis while contributing to the comprehension of the relation between the quality of eGovernment structures and the economic development based upon a set of pre-selected economic indicators. The development of the eGDS illustrated disparities in term of eGovernment development between the metropolises studied, some group of cases performed better than others, indicating room for improvement. To better understand the impact of eGovernment on the economic indicators selected, a statistical analysis has been conducted. While the application of the statistical analysis pointed at several degrees of correlation and some causal relationships between the variables and eGDS, it weakly supports the claims of the existing literature, indicating that further investigations shall be conducted. The embryonic stage of the eGovernment structure of French metropolises, explains the mild causality between the development of the eGovernment structure and the economic variables selected. Preliminary relationships have however been observed between the eGDS and the youth unemployment rate, the dynamism for employment and the entrepreneurship satisfaction. This work provides a theoretical and empirical basis for future research willing to understand the evolution of the electronic government structure of the French Metropolitan Park.http://www.ester.ee/record=b5145104*es

Non-linear effects and shock formation in the focusing of a spherical acoustic wave : Numerical simulations and experiments in liquid helium

The focusing of acoustic waves is used to study nucleation phenomena in liquids. At large amplitude, non-linear effects are important so that the magnitude of pressure or density oscillations is difficult to predict. We present a calculation of these oscillations in a spherical geometry. We show that the main source of non-linearities is the shape of the equation of state of the liquid, enhanced by the spherical geometry. We also show that the formation of shocks cannot be ignored beyond a certain oscillation amplitude. The shock length is estimated by an analytic calculation based on the characteristics method. In our numerical simulations, we have treated the shocks with a WENO scheme. We obtain a very good agreement with experimental measurements which were recently performed in liquid helium. The comparison between numerical and experimental results allows in particular to calibrate the vibration of the ceramics used to produce the wave, as a function of the applied voltage.Comment: 20 pages, 26 figures. Submitted to The European Physical Journal

Ab-Initio Calculations

Due to the difficulties found in the direct solution of the Schrödinger equation, different simplified approaches were proposed and are nowadays widely used. Among them, those most usually employed are the Hartree–Fock and the Density Functional Theory, which we revisit in the present chapter. The former makes use of nonstandard numerical approximations in order to calculate the wavefunction while circumventing the curse of dimensionality, whereas the latter involves the electronic density that is now defined in three dimensions but requires deeper analyses to retain the most relevant features present in the wavefunction description in a coarse 3D model

The Schrödinger Equation

The finest scale in the matter description consists of the one of quantum mechanics. In this chapter we revisit some valuable concepts of quantum mechanics, and more particularly the Schrödinger equation governing the time evolution of the so-called wavefunction, from which expectations can be easily derived. Another important output is the interatomic potentials responsible of the chemical bonds determining the structure and properties of materials. Even if the quantum framework is able to define the big picture, an important difficulty remains: the Schrödinger equation is defined in a highly multidimensional space and its solution is in most cases unattainable